Our general aim will be to continue biochemical comparisons between the 44K subunits of TL, Qa-2 and H-2 molecules in order to determine their degree of relatedness. We will determine whether there is polymorphism in Qa-2 and whether TL is similar to Ig H chains. We will determine whether there are regions of the TL and Qa-2 molecules which define "MHC-ness" vs "non-MHC-ness" both by NH2-terminal sequencing and by primary amino acid structure of those peptides which TL and Qa-2 share with H-2. Such information should give us significant insights into the evolutionary relationship and possible function of these MHC-linked gene products.